Short circuit-resistant polyethylene microporous film

Abstract

PCT No. PCT/JP96/03783 Sec. 371 Date Jun. 24, 1998 Sec. 102(e) Date Jun. 24, 1998 PCT Filed Dec. 25, 1996 PCT Pub. No. WO97/23554 PCT Pub. Date Jul. 3, 1997A microporous film comprising a high-density polyethylene and a linear copolymer polyethylene and having a terminal vinyl group concentration of 2 or more per 10,000 carbon atoms in the polyethylene, as measured by an infrared spectroscopic method.

What is claimed is: 
     
       1. A microporous film which comprises a high-density polyethylene or a linear copolymer polyethylene, said microporous film having: a) a terminal vinyl group concentration of about 2 or more per 10,000 carbon atoms in the polyethylene, as measured by an infrared spectroscopic method;   b) a density of about 0.90-0.98; and   c) a molecular weight range of about 100,000-3,000,000.   
     
     
       2. The microporous film according to claim 1, wherein the terminal vinyl group concentration is 5 or more per 10,000 carbon atoms in the polyethylene. 
     
     
       3. The microporous film according to claim 1, wherein the terminal vinyl group concentration is 6 or more per 10,000 carbon atoms in the polyethylene. 
     
     
       4. The microporous film according to any one of claims 1-3, wherein the weight-average molecular weight of the high-density polyethylene or linear copolymer polyethylene is 200,000-1,000,000. 
     
     
       5. A separator which comprises the microporous film of any one of claims 1-3. 
     
     
       6. A battery which uses the separator of claim 5 as a separator. 
     
     
       7. The microporous film according to claim 1, wherein the copolymer contains an α-olefin unit selected from the group consisting of propylene, butene, pentene, hexene, and octene. 
     
     
       8. The microporous film according to claim 7, wherein the α-olefin unit is present in an amount of 4 mol % or less based upon an ethylene unit of the polyethylene, whereby a fuse temperature is lowered. 
     
     
       9. The microporous film according to claim 1, wherein the high density polyethylene having a terminal vinyl group having about 2 or more per 10,000 carbon atoms is blended with a high density polyethylene having a terminal vinyl group having less than about 2 per 10,000 carbon atoms, whereby an average terminal vinyl group of the film does not fall below about 2 per 10,000 carbon atoms.